


Fun

by what_should_i_post_here



Category: Rise of the Teenage Mutant Ninja Turtles (Cartoon 2018), Teenage Mutant Ninja Turtles (TV 2012)
Genre: Anal Sex, Crossover, First Time, Kissing, M/M, Oral Sex, Plot What Plot/Porn Without Plot, Self-Indulgent, Svelte, Turtlecest (TMNT)
Language: English
Status: Completed
Published: 2019-03-17
Updated: 2019-03-17
Packaged: 2019-11-21 20:25:33
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 3,046
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/18147017
Author URL: https://archiveofourown.org/users/what_should_i_post_here/pseuds/what_should_i_post_here
Summary: After accidentally portaling himself to another universe, Leo shows an alternate Donnie what he's been missing out on.





	Fun

**Author's Note:**

> Just a self-indulgent smut fic of my favorite turtles from each show getting it on

"Hey, Not My Donnie! My Mikey was wondering..." Leo started walking into the lab. He stopped short when Donnie stood in front of him, preventing him from stepping any further into his lab. 

Donnie still didn't know this Leo well enough, or any of the other turtle brothers really, but it was safe to assume he wouldn't be safe around any of his projects. 

"Whoa," Leo whistled. "You really _are_ tall. Not as tall as My _Raph_ , of course. Though, your skinny figure does make you look taller."

"I uh..." Donnie began, crossing his arms. "I prefer 'svelte'."

"Svelte..." Leo nodded, running his tongue over his lips. "That's hot."

"Excuse me?"

"I bet your brothers get a kick out of your height thing, huh? Bet they like seeing you on your knees. Cutting you down to size."

"My...m-my knees?" Donnie questioned, backing into his desk, Leo closing in. 

"I'm sure someone as talkative as you gives amazing blowjobs," Leo smirked. "Like me."

The taller turtle looked absolutely flustered. "I...I don't... _we_ don't...do that."

"Oh," Leo seemed surprised for only a moment. "Really? Four teenage boys with raging hormones stuck together underground their whole lives and you guys haven't tried _anything_?"

Donnie blinked, and fell back into his swivel chair. He was slowly understanding just how different these alternate dimension turtles were compared to them. "N-no, of course not!" He sputtered out. "H...have you?"

Leo gave a nonchalant shrug, followed by a devilish smirk. 

"Wow, I-I..."

"What does it matter?" Leo questioned. "It isn't like we have many other options. Plus, we aren't technically related so... who cares?"

"Not related?"

"Different species," He explained slowly, considering it was fairly obvious. "Why, are you guys?"

"I...I don't know."

"So what's holding you back?"

"I..." Donnie's eyes darted nervously, accidentally landing on a photo frame on his desk before looking back at Leo. 

The blue turtle didn't miss it and immediately looked over. "Ah. You got a girlfriend."

"She's not my girlfriend!" Donnie shot back, on reflex.

"You... like her, though," Leo stated and Donnie merely shrugged, his face red.

"Who is she?"

"Her name is A-April."

"April O'Neil??" Leo roared with laughter and Donnie frowned. "What a strange universe."

"Oh, right, like yours is any-"

"Listen, Don," The other turtle interrupted, jumping onto the desk, crossing one leg over the other, and leaning forward. "I've only known you for a couple days...y'know, ever since I accidentally portal-ed me and my brothers into your dimension. " He waved off the last of his sentence like it was nothing. 

"Yeah, I've been meaning to talk to you about that-"

"But I've already seen and heard _plenty_." He smirked, leaning so close to Donnie's face that the genius could feel his breath, before he pulled back. "So I _know_ your other brothers are doing the dirty."

Donnie's eyes widened. "How dare-"

"And I _know_ the only reason you haven't been invited to join in on the fun is because your, let's face it, _ridiculous_ crush on this April is pushing you away from them."

"Now hold on just a minute!" Donnie fumed. It was one thing to hear all this from his family, but this turtle didn't know anything about him. He had no right-

Just as he was about to stand up and kick said turtle out of his lab, Leo held a hand to his plastron, keeping him down. "Trust me, Don. I meant what I said earlier. Your height is a major turn on, so it's nobody's fault your being left out, but your own."

"I'm not being left out of anything!" Donnie growled. "I don't want-"

Before he had a chance to speak again, Leo - with lightning speed Donnie could only describe as "cartoony" - climbed into his lap and kissed him squarely on the lips. 

Unable to react fast enough, Donnie let him finish, breathing out harshly when he finally pulled away. 

"Look, I'd hate to take away any of your brothers chance to be your first," Leo mused, playing with Donnie's mask tails. "But I'm also not gonna pass up the chance to be with a virgin again."

"I really don't-"

Leo kissed him again. He was more careful this time, precise. Taking his time to lick the other turtle's bottom lip. Pulling it into his mouth and suckling gently. 

Donnie squirmed under the blue turtle's ministrations and despite himself, let out a muffled churr.

Leo pulled back slightly, his lips still practically against Donnie's. "See? It's nice, right?"

"It's not... terrible?" Donnie admitted. 

Leo chuckled. "You're as stubborn as My Donnie was our first time."

They kissed again, only this time Leo went a step further, slowly poking the tip of his tongue between Donnie's lips. 

Having already surrendered at this point, Donnie allowed Leo entrance, moaning when their tongues touched. He decided it really wasn't _that_ bad. After all, it felt nice to be wanted this way. And kissing somebody was pretty enjoyable, no matter who it was coming from.

Feeling suddenly emboldened, the genius moved his hands, placing them at Leo's hips, when the blue turtle immediately pulled them off, and raised them over his head, grinning against Donnie's lips. 

"Hold on," He purred, giving a single lick to Donnie's mouth. 

"What, suddenly you're not in the mood?" The genius asked, his breath slightly ragged.

"Kissing is great," Leo said. "But I know something that's even better."

"And what's that exactly?"

As if to answer his question, Leo slid out of Donnie's lap and down to the floor. He carefully pulled apart the genius's thighs, settling between them before looking up seductively. 

"O...Oh...kay," Donnie stuttered, his throat closing up. "I'm uh, I'm not sure I'm ready for-"

Not giving the turtle a chance to finish, Leo leaned forward and swiped his tongue directly over Donnie's already bulging slit.

"Oh, shell..." He whimpered. 

Grinning, Leo repeated the action, running his hands along the inside of Donnie's thighs as he did so. 

The genius could barely keep his body steady. He hadn't even dropped down yet and he already felt like he was going to explode. His head was foggy, his body was burning. He clenched his hands tightly around the arms of his chair, wanting nothing more than to pull on Leo's masks tails. Pull him away, pull him closer...shell, he didn't even know.

But moving at this point seemed impossible, so he just let the blue turtle continue to suckle at his crotch until finally he released into the cool air of his lab, his hard member bouncing directly in front of Leo's face. 

"Not as big as My Raph," He observed, grabbing hold of it carefully and Donnie let out a hiss. "But definitely longer. What did you call it? Svelte?"

"That doesn't really work for...aaannnhhhh!" Donnie began before Leo pressed his lips to his pulsating head. 

He stayed there a moment longer, letting his tongue feel all around it before trailing down one side of his cock.

"Oh my fuuuuummm..." Donnie threw his head back, trying his hardest to muffle his noises. 

"God, you're loud," Leo mused. "Tall like Raph, stubborn as Donnie, and loud like Mikey..." He gave a gentle nip and Donnie shivered. "You're all my brothers wrapped in one."

Donnie threw his head back attempting to hold back another churr. "Wha... what about you? A-am I anything like you?"

Leo pulled off to answer, grinning. "You're sexy like me."

The genius choked out a laugh, a slight blush on his cheeks at the slight compliment. "You sure think...highly of yourself."

He merely shrugged. "Sexy enough to get you to forget about your feelings for Your April pretty quickly, anyway."

He winked and Donnie face went blank, letting out a soft groan as Leo continued his task. The purple turtle turned to the picture of April on his desk and bit his lip. 

It was true. Donnie barely thought about her the second Leo's lips were on him. Was it possible that all his brother's teasing, even his father's serious talks had gotten to him?

Was he just that horny for any sort of physical interaction or had his feelings for April dissipated a long time ago? Maybe ever since Casey entered the picture, Donnie had been slowly realizing what little chance he had with her.

He tried to think about the last time he'd fantasized about her, but came up blank. Had he just stopped all together? Or had other faces invaded his mind before bed?

He then thought of his brothers. Was it possible Leo was right about them fooling around together? Or was that just something this Leo had said to get into his shell?

Donnie looked down, watching Leo lifting his cock and swiping his tongue slowly along the underside. Donnie squeezed his eyes shut, moaning deeply. When he reopened his eyes, he imagined his own Leo between his legs, doing the same wonderful things this Leo was doing. 

Donnie shook his head, erasing the thoughts quickly and turned back to the photo of April. Still smiling, so blissfully unaware of the dirty deed going on in front of her. After Leo gave another long lick, Donnie groaned, reaching forward and forcing the picture to sit flat on its face. 

Then Leo leaned forward, taking more than half of Donnie's cock into his warm mouth. 

The genius groaned loudly, and finally let his hands move towards the other turtle, grabbing hold of the his head. Leo grinned around the hard member and hummed, the vibrations running up Donnie's cock, causing him to shake. 

"Damn," He muttered. Donnie rarely cursed. He never had any reason to. Even when a particular experiment went wrong, he stayed pretty quiet, relying on squeezing a stress ball Mikey had bought him a couple Christmases ago.

With his hands around Leo's head at the moment, squeezing didn't seem like the right thing to do. So when the blue turtle managed to take in another inch of his cock, and tighten his throat, the only thing Donnie could think you do was curse loudly, the sound echoing around the open space of his lab.

"This...is probably embarrassing," Donnie began, licking his lips. "But I'm not, uh...mmm...I-I'm not gonna last much longer."

Leo seemed to hear that as a challenge and as soon as the words left the genius, he pressed his lips even more tightly around Donnie's cock and began bobbing up and down the hard flesh as fast, yet carefully, as he could. 

His hands dug into his thighs, leaving indents Donnie would never be able to explain away and just as he was about to go down again, he looked up, locking eyes with the genius. 

Donnie looked back at him, his face hot, his breath ragged. After another long moment of eye contact, Donnie got ready to force the turtle to go back down, when Leo blew against the flesh still buried inside his mouth. 

The effect was instantaneous. Donnie's eyes widened and with another loud moan, he came, spilling his seed down the other turtle's throat. 

He could hear Leo swallowing everything and it made his face burn more. When the blue turtle finally pulled away, Donnie slumped back in his chair. 

"That was...I-I...oh, shit," He panted. 

"I know," Leo smirked. He stayed out of the genius's lap for a moment, letting him recover from his first blowjob, giving his neck gentle kisses as he waited for him to come to.

When he was certain Donnie was fine, he settled back into his lap. "Ready for Round two?"

"Round...two?" Donnie repeated, still slightly in a haze. 

"Of course. _You_ got off," Leo began, lapping at Donnie's lips like a kitten. "And now it's my turn."

Finally understanding, Donnie rose from the chair, causing Leo to step out of it. The genius stood on wobbly legs before falling to his knees. 

"Whoa there, Don," Leo said, picking the turtle back up. 

"You said you-"

"I appreciate it and maybe we'll have time for that later," Leo explained. "I have my sights set on a different area, though."

"And where might that..." Donnie began, before catching Leo's gaze directly on his backside. 

"Oh."

"Oh, so you're familiar with this," Leo grinned. "Considering how surprised you were about a blowjob, I thought I was going to have to walk you through sex."

"I've seen porn before..." Donnie frowned. 

"Yes, but _gay_ porn?"

The genius blushed furiously. 

"Oh, Don," Leo smirked. "It appears there's more to you than meets the eye."

"Yeah, well..." Donnie replied, gruffly. "Look, I know enough. Enough to know we need a certain item that I...don't..." The turtle trailed off, watching as Leo pulled the exact item from the pouch resting at his hip.

"You mean 'lube'?"

"Yes," Donnie choked out. 

"I always come prepared," He winked. "Now let's get started."

"W-where?"

Leo looked around. "You got a bed in here?"

The purple turtle managed a choked laugh. "No."

"Then I guess the desk will have to do."

"How...?"

"Turn around and bend over the top, Don." Leo explained slowly, carefully. Donnie did as he was told, cheeks burning at how exposed the position made him feel. 

"Good turtle," Leo smirked, running his hand from the top of his carapace and down, giving Donnie's tail a gentle flick at the end. 

The genius gave a quiet "mmff" at the gesture, gripping the desk for what was to come.

The blue turtle continued massaging the taller's twitching appendage, enjoying the sounds coming from him as he did so. "Way more sensitive than My Donnie. And that's saying a lot, considering he's a soft-shell."

"You just gonna...mmm...play with my tail the w-whole time?"

"You sure are impatient for someone who's already come," Leo mused. Then, after a beat. "Shell, you're hard again, aren't you?"

Donnie remained silent, his face beet red.

Leo chuckled, biting his lip. "That's hot."

"Just get on with it."

"Don't have to tell me twice," The blue turtle grinned, pulling his fingers away and applying a small amount of lube. He still took his time, taking pleasure in the annoyed grunts from Donnie as he did so. 

Then, with no warning, his finger brushed against the genuis's puckered entrance, causing him to spasm, his entire lower half shooting up into the air. 

Leo chuckled again. "Too much?"

"Just wasn't prepared," Donnie huffed out. "Wasn't expecting it to feel so..."

"Good?"

"Tingly."

"Oh-ho, it's about to get better," Leo winked. Then, placing one hand in the center of Donnie's back, he returned to the sensitive hole, carefully dipping his finger inside. 

The purple turtle gripped the desk even harder.

Leo waited a moment, watching his arm muscles tense and then relax, pushing his finger in further. He managed to get about a knuckles way in, before pulling out and repeating the gesture. 

Donnie hissed. "Can... can you use more lube, please?"

Leo dramatically rolled his eyes. "Sure thing, princess."

Pulling out, Leo did just that, returning back to the slightly lubed up entrance. After a few more minutes, Donnie's tense form relaxed and when he appeared to be humping back on Leo's finger, the blue turtle grinned.

He pulled away from Donnie's body, enjoying the groan of protest that came with it and began lubing up his cock, which had dropped down sometime during the detailed fingering.

"You ready for the fun part?" He asked, twiddling his fingers as his hands rested perfectly at Donnie's hips. 

The genius chuckled. "What? The rest of this hasn't been fun for you?"

"Not as fun as it's about to be."

"Well then, what are you waiting for?"

Leo grinned, then as carefully as he could, considering just how horny he was at this point, began pushing himself inside the taller turtle. 

Donnie buried his face into the desk, moaning louder than he had this whole time.

After a few pull outs and ins, Leo managed to fit completely inside Donnie. He waited a few moments longer, then pulled out again, only to ram right back inside.

"Fuck!"

"Hah," Leo puffed out. "Like that?" He didn't wait for an answer, repeating the movement three or four more times, when Donnie suddenly froze underneath him. 

After a long moment of silence, he breathed out. "Do that again."

"What?" Leo asked innocently. "Oh, you mean this?" He pulled out and thrust right back in, connecting with his prostate for the second time. 

"Fuck, yes!" Donnie moaned out. "God, yes. Keep going!"

"Yeah?" Leo continued thrusting erratically into the pinned turtle, tightening his grip on Donnie's hips. "Knew you'd like it, Don. Want it to be like this all the time, huh? Except with your brother's on the other end. Fucking you, sucking you, making you cum all over your lab floor?"

Almost as if on cue, Donnie did just that, coming for the second time, all over his legs and the front of his desk. "Yes..." He muttered, suddenly very tired, even as Leo continued to ram into him. 

It was short-lived, however, because as soon as Donnie released, his backside put Leo's cock in a death grip, causing the blue turtle to spill his seed.

He relaxed then, laying over the still pinned down turtle, while they both attempted to regain their breath. 

"You were right," Donnie managed to say, his voice almost a whisper. "That _was_ fun."

"I'm never wrong," Leo gave a smug grin, kissing the back of Donnie's neck. 

"So, you... you really think my brothers..."

Before he had a chance to finish, said turtles could suddenly be heard just outside the lab.

Donnie's eyes widened, glancing over at Leo. 

The blue turtle shrugged. "Now's your chance to find out."

Leo got up, giving Donnie the chance to turn around and stand up himself, just as his brothers opened the door.

They mindlessly stepped inside, lost in a random conversation, when one by one, they took in Donnie's state: Face red, dick still hanging out, cum dripping down his legs...

The brothers froze in place, unsure what to do or say, when Leo strolled past them, towards the door, a smug grin on his face. 

He winked. "He's all yours."


End file.
